diff --git a/ROADMAP.md b/ROADMAP.md
index 1edc66f47a9386..017213fb514ca5 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -41,8 +41,9 @@
 - [ ] -skip-unused on by default
 - [ ] 64/32 bit int depending on arch (will remove array.len limitation on 64 bit systems)
 - [ ] `copy()` builtin function (e.g. for easier conversion from `[]Foo` to `[4]Foo`)
-- [ ] Lambdas: `a.sort(|a, b| a > b)`
+- [x] Lambdas: `a.sort(|a, b| a > b)`
 - [ ] Custom attributes.
+- [ ] `arr.first() or { }` like `arr[0] or { }`
 
 ## [Version 1.0]
 
diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index 8c0185163abba8..32b658a3c0d79b 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -716,7 +716,7 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 				if field.typ.is_ptr() && !field.typ.has_flag(.shared_f)
 					&& !field.typ.has_flag(.option) && !node.has_update_expr && !c.pref.translated
 					&& !c.file.is_translated {
-					c.warn('reference field `${type_sym.name}.${field.name}` must be initialized',
+					c.error('reference field `${type_sym.name}.${field.name}` must be initialized',
 						node.pos)
 					continue
 				}
@@ -840,7 +840,7 @@ fn (mut c Checker) check_ref_fields_initialized(struct_sym &ast.TypeSymbol, mut
 		}
 		if field.typ.is_ptr() && !field.typ.has_flag(.shared_f) && !field.typ.has_flag(.option)
 			&& !field.has_default_expr {
-			c.warn('reference field `${linked_name}.${field.name}` must be initialized (part of struct `${struct_sym.name}`)',
+			c.error('reference field `${linked_name}.${field.name}` must be initialized (part of struct `${struct_sym.name}`)',
 				node.pos)
 			continue
 		}
diff --git a/vlib/v/checker/tests/reference_field_must_be_initialized.out b/vlib/v/checker/tests/reference_field_must_be_initialized.out
index 4e298481455f3d..b99c69f61d8327 100644
--- a/vlib/v/checker/tests/reference_field_must_be_initialized.out
+++ b/vlib/v/checker/tests/reference_field_must_be_initialized.out
@@ -1,4 +1,4 @@
-vlib/v/checker/tests/reference_field_must_be_initialized.vv:8:7: warning: reference field `Node.next` must be initialized
+vlib/v/checker/tests/reference_field_must_be_initialized.vv:8:7: error: reference field `Node.next` must be initialized
     6 | 
     7 | fn main(){
     8 |     n := Node{ data: 123 }
diff --git a/vlib/v/checker/tests/struct_field_reference_type_err.out b/vlib/v/checker/tests/struct_field_reference_type_err.out
index 8e168619d5faac..534556e123f45d 100644
--- a/vlib/v/checker/tests/struct_field_reference_type_err.out
+++ b/vlib/v/checker/tests/struct_field_reference_type_err.out
@@ -1,11 +1,4 @@
-vlib/v/checker/tests/struct_field_reference_type_err.vv:12:16: warning: reference field `Animal.duck.age` must be initialized (part of struct `Duck`)
-   10 |
-   11 | fn main() {
-   12 |     mut animal := Animal{
-      |                   ~~~~~~~
-   13 |         ageee: 20
-   14 |     }
-vlib/v/checker/tests/struct_field_reference_type_err.vv:12:16: warning: reference field `Duck.age` must be initialized
+vlib/v/checker/tests/struct_field_reference_type_err.vv:12:16: error: reference field `Animal.duck.age` must be initialized (part of struct `Duck`)
    10 |
    11 | fn main() {
    12 |     mut animal := Animal{
diff --git a/vlib/v/checker/tests/struct_ref_fields_uninitialized_err.out b/vlib/v/checker/tests/struct_ref_fields_uninitialized_err.out
index 400f509bdc818a..1636e861f19ab4 100644
--- a/vlib/v/checker/tests/struct_ref_fields_uninitialized_err.out
+++ b/vlib/v/checker/tests/struct_ref_fields_uninitialized_err.out
@@ -1,31 +1,11 @@
-vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:25:7: warning: reference field `Outer.c1.b` must be initialized (part of struct `ContainsRef`)
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:25:7: error: reference field `Outer.c1.b` must be initialized (part of struct `ContainsRef`)
    23 |
    24 | fn main() {
    25 |     _ := Outer{}
       |          ~~~~~~~
    26 |     _ := Struct{}
    27 | }
-vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:25:7: warning: reference field `ContainsRef.b` must be initialized
-   23 |
-   24 | fn main() {
-   25 |     _ := Outer{}
-      |          ~~~~~~~
-   26 |     _ := Struct{}
-   27 | }
-vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:25:7: warning: reference field `Outer.c2.b` must be initialized (part of struct `ContainsRef`)
-   23 |
-   24 | fn main() {
-   25 |     _ := Outer{}
-      |          ~~~~~~~
-   26 |     _ := Struct{}
-   27 | }
-vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:26:7: warning: reference field `Struct.ref2` must be initialized
-   24 | fn main() {
-   25 |     _ := Outer{}
-   26 |     _ := Struct{}
-      |          ~~~~~~~~
-   27 | }
-vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:26:7: warning: reference field `EmbedStruct.ref2` must be initialized
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:26:7: error: reference field `Struct.ref2` must be initialized
    24 | fn main() {
    25 |     _ := Outer{}
    26 |     _ := Struct{}
diff --git a/vlib/vweb/vweb.v b/vlib/vweb/vweb.v
index 8311c2f4df87c9..16278b4520e551 100644
--- a/vlib/vweb/vweb.v
+++ b/vlib/vweb/vweb.v
@@ -315,6 +315,7 @@ pub fn (mut ctx Context) redirect(url string) Result {
 
 // Send an not_found response
 pub fn (mut ctx Context) not_found() Result {
+	// TODO add a [must_be_returned] attribute, so that the caller is forced to use `return app.not_found()`
 	if ctx.done {
 		return Result{}
 	}